1. Field of the Invention
The present invention relates to a blood sampler of the suction type useful for sampling from a human a necessary amount of blood to be subjected to various blood tests, by thrusting a needle into the skin of the human and applying a vacuum of a certain degree to the skin to draw the blood sample into the device.
2. Description of Prior Art
Each of the known so-called lancet injectors generally comprises a pressable end and a blade opposed thereto and having an acute end capable of piercing human skin. By gently striking the pressable end, the acute end will pierce, for example, the skin of a finger. A small amount of blood will ooze out of the skin to be taken into a container by using a pipette or the like and is then subjected to necessary tests. There are many fine blood vessels in a finger so that a finger can be pressed to cause a small drop of blood to ooze therefrom. Since fingers are more sensitive to pain, an upper arm, abdomen or thigh have recently been used for blood sampling. Similar devices are also used in the latter case, and an example thereof is disclosed in Japanese Patent Publication Kokai No. Sho-62-38140. This device comprises a cylindrical housing and a lancet support, which has a gasket or the like slidably accommodated in the housing. Springs will retract the lancet support to thereby reduce air pressure in the housing so that it sucks a blood sample automatically and immediately after a lancet pierces the skin.
The gasket in the prior art device fixed to the lancet support is in airtight contact with the inner peripheral surface of the housing. Friction between the gasket and the inner surface will lower the thrust speed of the lancet or needle, thereby increasing pain. Further, the lancet support is automatically held in place where the skin sticks to the device, due to the reduced air pressure. When the housing is taken off, the skin will spring back and ambient air will rush into the housing. In such a case, the oozed blood scatters and is lost, and an additional amount thereof is needed.